The present invention relates to medical clips and more particularly to sterilisation or ligation clips suitable for occluding blood vessels.
Known clips are made from metal upper and lower jaws hinged together, the jaws being hinged to allow the jaws to be opened to encompass a tube or blood vessel. Usually the jaws are provided with silicon rubber lining. The clip is closed by deformation of the upper jaw which is curved, the deformation lengthening the upper jaw which is then latched under a latch on the lower jaw. Such a clip is described in U.S. Pat. No. 4,489,725 (FILSHIE).
A problem with such clips is that when made of a material such as titanium, the upper jaw or gate is work hardened when initially deformed into the curved shape.
The consequence of the work hardening of the upper jaw material is that it requires greater force to overcome the resistance in the material caused by such work hardening than is necessary to close the tube or blood vessel structures occluded or ligated by the clip.
This can result in one of two possible malfunctions of the clip.
Firstly, the clip can fail to close even if the correct closure pressure is applied because the upper jaw can spring back because additional strength is required to fully lengthen the upper jaw. The clip therefore fails.
The second condition is that sufficient strength is applied to straighten the upper jaw, but this force has to be greater than is required to occlude or ligate. In this case the tube or blood vessel can be severed creating a possible emergency situation.
It is an object of the present invention to provide a clip which obviates the above problem.
The present invention, therefore, provides a medical clip comprising elongate upper and lower jaws at least said upper jaw being metallic, said lower jaw being hinged by connection to said upper jaw at a first end of said elongate structure and said lower jaw being formed with latch means at said other end, said upper jaw being formed curved in a non operated condition and said upper jaw being constructed to be deformable under applied load to thereby extend the effective length of said upper jaw to enable said upper jaw to latch under said latch means in said lower jaw when in an operated condition and in which said upper elongate jaw is provided with stress relief means in an intermediate area along said length of said upper jaw.
Preferably, said stress relief means comprises a hole extending through said upper jaw.
Preferably, both said upper and lower jaws are metallic.
In a preferred embodiment at least one of said jaws is lined internally with a silicone rubber lining.
More preferably, both said jaws are internally lined with a silicone rubber lining.
In a specific embodiment said upper jaw comprises a first substantially straight portion situated at said first end nearest to said hinge, a second curved portion and a third substantially straight portion, said third portion providing a latching surface for engagement with said lower jaw and in which said hole is formed in said second curved portion.
In a preferred embodiment, the second curved portion comprises a complex curvature, including two sections of different radii of curvature.